Tapered Optical Fiber Probe Assembled with Plasmonic Nanostructures for Surface-Enhanced Raman Scattering Application

Transcription

1 Supporting Information Tapered Optical Fiber Probe Assembled with Plasmonic Nanostructures for Surface-Enhanced Raman Scattering Application Zhulin Huang, Xing Lei, Ye Liu, Zhiwei Wang, Xiujuan Wang, Zhaoming Wang, Qinghe Mao, and Guowen Meng*,, Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei , P. R. China University of Science and Technology of China, Hefei , P. R. China Anhui Provincial Key Laboratory of Photonics Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei , P. R. China * Guowen Meng. gwmeng@issp.ac.cn. KEYWORDS plasmonic nanostructures, tapered fiber probe, electrostatic attraction, surface-enhanced Raman scattering, detection S-1

2 Figure S1. Left column: SEM image of a Ag nanocube sensitized tapered fiber probe (8.2 o ). Middle column: the SEM images (a, c, e, and g) showing the distribution of Ag nanocubes at different sites (indicated by the blue marks) of the tapered SERS fiber probe. Right column: SEM images (b, d, f, and h) demonstrating the corresponding close-up views. S-2

3 Figure S2. (a)-(d) SEM images of the APTES functionalized fiber probe surface with immersion duration of 0.5 h, 1 h, 2 h and 4 h in Ag-nanocube suspension respectively. All scale bars indicate 500 nm. S-3

4 Figure S3. (a) TEM images of core-shell nanorods with varied shell thickness under varied addition amount of AgNO 3 precursor: 0.4 ml, 0.6 ml, 0.8 ml, 1 ml, 1.5 ml, 2 ml, 2.5 ml, and 3 ml. Here the "0 nm" sample indicates Au-nanorod. (b) The visible near infrared spectra (with the longitudinal mode from left to right) of the Au@Ag core-shell nanorods dispersed in deionized water indicated in Figure S3a (from left to right). (c) SERS spectra of 2-naphthalenethiol adsorbed on the Au@Ag core-shell nanorods with varied Ag shell thickness, indicating a shell thickness dependent SERS intensity versus the 785 exciting line. S-4

5 Figure S4. CTAB protected positively charged Au-nanorods assembled on a 8.2 o tapered fiber probe using CEOS as the adsorbing agent. (a) The optical image. (b), (c) The SEM images of Au-nanorods decorated fiber probe surface at varied magnifications respectively. (d) TEM image of the Au-nanorods used for decoration of the fiber probe. S-5

6 Figure S5. The dark Raman scattering noise generated by the fibers measured in air (upper curve) and in water (lower spectrum) under an effective laser power of 20 mw. S-6

7 Figure S6. (a) and (b) are the FEM simulations of the electromagnetic field enhancement of a Agnanocube exposed in water and vacuum medium respectively. (c) and (d) represent the FEM simulations of the electric field enhancement of Au nanosphere and Au nanorod exposed in vacuum respectively. (e) FEM modeling of two coupled Au@Ag core-shell nanorods of 1 nm gap with varied Ag-shell thickness. (f) The electric field distribution of two coupled Au@Ag core-shell nanorods with 3 nm Ag-shell (left image) and 10 nm Ag-shell (right image) respectively. Here the diameter of Au nanorod is 10 nm and the length is 40 nm. The longitudinal thickness of the Ag-shell is set as 4 nm. S-7

8 Figure S7 Optical images of several batches of naked fiber probes with varied taper angle as indicated in the image. All scale bars represent 500 nm. Figure S8 SERS spectra measured separately in the p-atp (10-5 M) analyte solution from one batch of Ag-nanocubes-sensitized fiber probe (10.1 o ). The laser power is 20 mw. S-8

9 Figure S9 Comparison between the SERS spectra of p-atp (10-5 M) adsorbed on Ag nanocubes decorated 8.2 o tapered fiber (upper curve) and flat fiber probe (lower curve). All the spectra were measured in solution at 20 mw. S-9

10 Figure S10. UV-Vis-NIR absorbance spectra of the four nanostructure suspensions. S-10